Device for detecting relative speed of inner and outer rings for an ABS braking system

ABSTRACT

A device for detecting speed in a braking system between two relatively rotatable elements, such as, the inner and outer rings of a roller bearing used to support a vehicle wheel. The device includes a first deflector mounted on one of the bearing rings having a magnetized ring member and a plurality of radially outwardly facing poles separated by non-magnetized spaces and a serrated annular member having a plurality of radially inwardly facing ribs. The device further includes a second deflector integral with a fixed ring of the bearing having at least one magnetic sensor engageable between the two bearing rings and spaced to intersect the magnetic fields to produced a plurality of signals per revolution. The signal produced by the sensor has a frequency proportional to the relative speed of the inner and outer bearing rings.

FIELD OF THE INVENTION

The present invention relates to improvements in devices capable ofdetecting rotational speed of two relatively rotatable elements such asthe support elements of a vehicle wheel.

BACKGROUND OF THE INVENTION

The need for installation of special control circuits in automotivevehicles is increasing. Typical of the type of control circuitspresently in automotive vehicles include so-called anti-lock brakingsystem (ABS) which prevent the locking of the vehicle wheels duringbraking, ASR Systems, which ensure correct traction of motor vehicles,devices for detecting speeds such as tachometers and devices formeasuring the distance travelled such as odometers. At present thesedetection systems are comprised of basic component such as phonic rings,detecting sensors, on-board computers and hydraulic systems. The phonicring is usually a serrated ring mounted on the rotating part desired tobe monitored and the sensor comprising a passive or active type ismounted on the fixed part of the frame and confronts the serrated zoneof the phonic ring at a predetermined distance. Electronic signalsemanating from individual sensors are transmitted to the on boardcomputer which in the case of the ABS computes the differences in thespeed of wheels of the vehicle.

Passive sensors currently utilized operate by variation in reluctanceand require no input. However, sensors of this type must be mountedexternally to the bearing and are thus unprotected against possibleimpacts, contaminating agents and other hazards. This type of sensor isparticularly sensitive to metal particles resulting from wear of thebrakes near the sensor themselves and to the elevated temperaturesdeveloped by disc brakes. They also require appropriate calibrationduring the mounting phase by the user. It has also been found that thesensors are incapable of detecting rotational speeds down to zero milesper hour and thus cannot be use for tachometric and odometricmeasurements.

SUMMARY OF THE INVENTION

With the foregoing in mind, it is an object of the present invention toprovide a detection device characterized by novel features ofconstruction and arrangement which eliminates the shortcomings of thedevices presently in use discussed above. Specifically, the inventionrelates to a detection device capable of detecting the relativerotational speeds of the support elements of a vehicle wheel whichconsist of an initial deflector or ring formed integrally with arotating ring in the bearing and which carries twin magnetized ringswith pairs of poles of opposite signs, between which a sensor of themagnetic type carried by a second deflector or support integral with thefixed ring of the bearing is operationally inserted. The magnetic sensoris located between the n polar expansions, the number of which conformsto the pairs of opposing poles of the twin magnetized rings.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects of the present invention and the variousfeatures and details of the operation and construction thereof arehereinafter more fully set forth with reference to the accompanyingdrawings, wherein:

FIG. 1 is a sectional view of a speed detecting system in accordancewith the present invention;

FIGS. 2 and 3 show partial perspective views of the system in twotypical applications; and

FIG. 4 shows a modification of the system shown in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings and particularly to FIG. 1 thereof, thereis shown a bearing assembly generally designated by the reference B forsupporting the wheel of the vehicle comprising usual inner and outerrelatively rotatable rings 11 and 15 respectively and a plurality ofrolling elements, balls in the annular space between the rings.

Speed sensing device in accordance with the present invention includes aprimary support 10 consisting of an annular U-shaped element mounted onthe rotating ring 11 of the bearing assembly. The support 10 hasillustrated in FIGS. 2 and 3 carries a magnetized ring 12 on one of itsflanges, the inner flange 10 consisting of poles of alternating sign NSNas illustrated in FIG. 2. The magnetized ring 12 may also consist ofpoles of the same sign and in NNN or SSS as illustrated in FIG. 3. Asserrated ring having a plurality of radially inwardly dependingserrations 16 confront and overlie the magnetized portions of ring 12about the circumference of the outer axial leg 10b of the primarysupport 10. A lubricated seal made of a resilient material is mounted inthe outer ring 15 and sealingly engages the support 10 in a mannerpermitting relative rotation of the inner and outer rings 11 and 15.

The detection system of the present invention further includes a secondsupport mounted on the outer ring 15 carries a magnetic sensor 13operating by the Hall-effect or of the magnetoresistance type. Thesensor as illustrated engages in the annular gap between the magnetizedring 12 and the serrated ring 16.

Magnetic sensor 13 with its integrated control of electronics issupplied by the on-board voltage of the motor vehicle. The signalfurnished to the on-board computer is a function n of the changes in themagnetic field to which the element is subjected. The Hall-effect sensorcan be of the linear, unipolar, bipolar or bipolar with memory type.

As best illustrated in FIG. 2, sensor 13 is immersed in the magneticfield created by n magnets 12 and is accompanied by metal serrations 16facing them.

Magnetized ring 12 can be of rubber impregnated with magnetic particlesand fixed or vulcanized to a support ring, which can also constitute theclosure element of the magnetic flux. Alternatively, ring 12 can be ofplastic impregnated with magnetic particles or can consist of sinteredmaterials or even of elementary magnets.

The material in which this is effected can have either isotropic oranisotropic characteristics.

The magnetic ring 12-metal serrated ring 16 assembly can be eitheraxially configured as shown in FIG. 1, or radially configured as shownin FIG. 4, without causing any change in the advantages of theinvention.

The rotation of deflector 10 with the two rings 12 and 16 integral withit induces variations in the magentic fields in amplitude and sign inHall effect-magnetic sensor 13.

The signal furnished by the sensor has a frequency proportional to thespeed and, assuming the appropriate design of the electronics formingpart of the Hall effect sensor 13, is sent to the on-board computer.

The sensor system can also consist of two or more magnetic sensors 13with their integrated electronics to facilitate dectection of therotation, using fewer magnetic poles but with each sensor operating atthe same frequency.

For this application, the sensors should be spaced by an appropriateangle, as shown schematically in FIG. 3.

The same multisensor system can also be used to detect the direction ofrotation of the wheel by providing it with a supplementary output.

What is claimed is:
 1. A device for detecting speed in a braking systembetween inner and outer rings of a roller bearing used to support avehicle wheel, a first deflector mounted on one of the bearing ringscomprising a magnetized ring member mounted on said deflector having aplurality of poles separated by non-magnetized spaces and a serratedring member having a plurality of radially inwardly directed ribs facingthe plurality of poles of the magnetized ring member to define aplurality of radially directed magnetic fields, a second deflectorintegral with the other bearing ring having at least one magnetic sensorengageable between the two ring members and spaced to intersect each ofsaid plurality of radially directed magnetic fields to produce aplurality of signals per revolution, wherein the signal produced by saidsensor has a frequency proportional to the relative speed of the innerand outer bearing rings.
 2. A device as claimed in claim 1, wherein themagnetic sensor is of the Hall-effect.
 3. A device as claimed in claim1, characterized in that the sensor is of the magnetoresistance type. 4.A device as claimed in claim 1, characterized in that the poles of themagnetized ring are of alternating sign and alternate withnon-magnetized zones.
 5. A device as claimed in claim 1, wherein thering members extend axially defining a radial space therebetween andwherein said magnetic sensor projects axially into said radial space. 6.A device as claimed in claim 1, wherein the ring members extend radiallydefining an axial space therebetween and wherein said magnetic sensorprojects radially into said axial space.
 7. A device for detecting speedin a braking system between inner and outer bearing rings used tosupport a vehicle wheel, comprising a first deflector mounted on one ofthe bearing rings including a magnetized ring member with polesseparated by non-magnetized spaces and a serrated ring member having aplurality of serrations facing the poles of the magnetized ring member,a second deflector integral with the other bearing ring having at leasttwo magnetic sensors operatively inserted between the two rings membersand spaced from one another such that only one sensor at a time isradially aligned with a pole and a serration wherein the signal producedby said sensor has a frequency proportional to the relative speed of theinner and outer bearing rings.
 8. A device as claimed in claim 7,wherein the magnetic sensors are spaced by multiples or fractions ofhalf the pitch between adjacent poles.